Estimation of gestational age during the first trimester by real-time measurement of fetal crown-rump length and biparietal diameter.
A series of 237 patients in the first trimester of pregnancy were examined to derive normal growth curves for fetal crown-rump length (CRL) and biparietal diameter (BPD) using sector scanner real-time ultrasound equipment. Conventional B-scan CRL measurements were obtained from 50 of these patients: In 41 (82%), the values fell within a range +/- 5 mm of those of real-time. Another group of 97 patients between 7 and 13 wk of gestation was then examined in a blind trial to confirm the accuracy of real-time measurements in estimating gestational age. An estimate was made in 95% of cases to within 4.6 days with CRL and to within 5 days with BPD. A similar comparison was made with both of these dimensions using a comparative nomogram, giving a prediction within 3.9 days in 95% of cases. This method is now used routinely.
D000886:Anthropometry; D002508:Cephalometry; D005260:Female; D005333:Fetus / Q000033:anatomy & histology; D005865:Gestational Age; D006801:Humans; D008598:Menstruation; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D014463:Ultrasonography